Dissolving cadmium metal in sulphuric acid in the presence of metallic iron



Fatented Mar. 6, 1934 UNITED STATES PATENT QFFICE DISSGLVING CADMIUMMETAL IN SUL- PHURIC ACID IN THE PRESENCE OF METALLIC IRON No Drawing.Application November 8, 1932, Serial No. 641,761

1 Claim.

The present invention relates to a process of dissolving metalliccadmium in hot, dilute sulphuric acid and is characterized by the factthat the operation is carried out in the presence of s metallic iron.

It is well known that ordinary commercial slabs of metallic cadmium oreven feathered cadmium metal dissolve extremely slowly in hot, dilutesulphuric acid, as a matter of fact, I found for instance that only 6%of cadmium metal was dissolved when feathered cadmium was boiled for 18hours in an excess of 20% sulphuric acid.

I have found that if metallic iron is present in the reaction mixture ofsulphuric acid and 1 cadmium metal the rate of attack of the cadmium isconsiderably accelerated, whereas the iron is only dissolved to a smallextent.

The following is an example of how I have operated my novel process:

I have, for instance, heated cadmium metal in boiling 20% sulphuric acidin which has been immersed a piece of sheet steel and found that in 48hours 90 parts of cadmium metal were dissolved whereas only 6 parts ofthe iron had gone into solution.

Strange enough, I found also that iron salts, such as ferrous sulphateor other metals, such as copper, when present in the sulphuric acid donot materially affect the rate of attack of the sulphuric acid upon thecadmium metal.

The cadmium sulphate solution obtained according to my novel processcontains small amounts of ferrous sulphate. This, however, can beremoved from the cadmium sulphate solution by well known means. Thispurification step does not counterbalance the great saving efiected bythe increased rate of attack by the presence of metallic iron in thereaction mixture.

I claim:

The process of dissolving cadmium metal which comprises boiling metalliccadmium and iron in dilute sulfuric acid solution.

HARRY P. CORSON.

